Thanks so far for your responses. I do plan to have a dehumidifier in the basement, and it will be drained into the sump pump. Getting it off the ground is a good idea- thanks.

bigcountry, do you know how much a humidity guage costs? Also, would I put it inside the gun safe?

Does anybody have their safe in a room on the upper level? I have a Cannon 22 gun safe, which weighsabout 500 pounds. I would prefer to have it upstairs, but don't know if it would be a bad idea due to the weight.